Manufacture of trialkyl phosphites



. Yam- 1 l MANUFACTURE TRIALKYL PHOSPHITES Harold Coates, Wombourne',and William Hubert Hunter, Shepton Mallet, England,'assignors toMinister of Supply, in Her Majestys Government of the United Kingdom ofGreat Britain and Northern Ireland, London, England H 1 U if v' Drawingt Application septemlier 9, 1952 priority; applicationGreat BritainDecember 12, 1951 j reclaims. Cl. 260-461 t l laims Thisinventionrelates t- .the manufacture, of trialkyl phosphites in animproved manner.

We have shown in a'co-pending patent application (No. 308,726, nowPatent No. 2,880,223) .that the production of the cuprous halidecomplexes of trialkyl phosphites from cuprous halide, an alkanol andphosphorus trihalide i venient is phosphorus trichloride.

According to the present invention a process for the manufacture oftrialkyl phosphites is provided wherein a trialkyl phosphite-cuproushalide complex is first produced and the said complex is subjected totreatment by which it is decomposed or decomplexed to liberate thetrialkyl phosphite which is then separated from the reaction product.

Thus, according to the invention, by heating a trialkyl phosphitocuprouschloride complex under vacuum and condensing the vapours evolved weobtain the trialkyl phosphite in good yield. An important advantage ofthis process is that the cuprous chloride is regained and is in a formsuitable for re-use in the preparation of a further batch of cuprouschloride complex, without further treatment.

The trialkyl phosphite distilled off in this way contains a minorproportion of dialkyl alkanephosphonate which can be removed byfractionation.

Further, in accordance with the invention, we have also found that theabove-mentioned cuprous halide complex may be decomposed by chemicalmeans. Examples of such means are (1) heating the complex suspended inan inert solvent such as ethyl acetate with a finely divided metal whichis capable of reducing the cuprous halide to metallic copper, forexample zinc dust. (2) Alternatively, the decomposition may be carriedout by refluxing in an inert solvent such as the alcohol correspondingto the ester groups of the phosphite in the presence of a reagentcapable of transforming the cuprous halide into another copper saltwhich does not complex with the phosphite. As an example, a trimethylphosphite complex may be refluxed with anhydrous sodium sulphide inmethanol.

(3) A further alternative method of decomplexing the cuprous halideaccording to the invention consists in treating the complex with areagent itself capable of forming a complex with for instance cuprouschloride which is more stable than the trialkyl phosphite-cuprouschloride complex, thus displacing the phosphite. As examples of -p Ratntedalulya28, 1.959

such complexing agents we may cite pyridine and methyl cyanide. V V

The invention will now following examples: r Example 1.Trimethyl;phosphite-cuprous-- chloride complex (83 gms.) wasspread in a thinlayer .on the bot tom of a flask and heated in an oil bath up toamaximum temperature of 220? C., under-reducedpressure (0.1 to 0.5 mm.Hg). The trimethyl phosphite commenced to distill off slowly atapproximately 120?, C.; and .wascollected in a condensing system cooledto; C." The amount of trimethyl phosphite, contaminated with dimethylmethanephosphonate, recovered was 207gm. The recovered cuprous chloride"( 63 gn-r.) was used-again in the. preparation of more complexcycle of. operations was carried through three times without addingfresh cuprous chloride. v l: Example 2.Trimethyl; phosphite-cuprouschloride complex (50 gm.) in ethyl acetate (200 cc.) wasrefiuxed ,forseveral hours withicommerc ial zine-dust (3O gun). The sludge of copper.and zinc was filtered off and the ethyl acetate solution fractionatedgiving trimethyl phosphitein70%yield. I 2 Example 3.--A suspension oftrimethylgphosphitercur prous chloride complex (21 inmethanol; (50 cc.)was treated gradually with stirring with a solution of anhydrous sodiumsulphide (4 gm.) in methanol (200 cc.). A black precipitate was formedwith slight evolu tion of heat. At the end of the addition the mixturewas refluxed for half an hour and then filtered. The filtrate wasstripped of methanol and the residue distilledvgiving 6 gm. trimethylphosphite, B.P. C. (60% yield).

Example 4.Trimethyl phosphite-cuprous chloride complex (25 gm.) wastreated with methyl cyanide and the mixture distilled. Some methylcyanide distilled oif,

be described with the aid ofthe followed by trimethyl phosphite (7 gm),B.P. approximately 110 C.

We claim:

1. Process for the production of lower unsubstituted trialkylphosphites, which process comprises reacting a cuprous halide withphosphorus trichloride and with a lower unsubstituted alkanol to producea cuprous halidetrialkyl phosphite complex and subjecting the saidcomplex to controlled decomposition under conditions which liberate thetrialkyl phosphite.

2. Process which comprises subjecting a cuprous halidetrialkyl phosphitecomplex to chemical decomposition by a reagent which removes the cuproushalide component of the said complex and liberates the trialkylphosphite.

3. Process which comprises reacting a cuprous halidetrialkyl phosphitecomplex with a finely divided metal capable of reacting with the cuproushalide component of the complex to liberate the trialkyl phosphite.

4. Process which comprises decomposing a cuprous halide-trialkylphosphite complex by heating the said complex with zinc dust to liberatethe trialkyl phosphite.

5. Process which comprises decomposing a cuprous halide-trialkylphosphite complex by a reagent which reacts with the cuprous halidecomponent to form a copper compound which does not complex with thetrialkyl phosphite and thereby liberates the said trialkyl phosphite.

6. Process which comprises decomposing a cuprous halide-trialkylphosphite complex by a soluble reactive sulphide to liberate thetrialkyl phosphite.

7. Process as claimed in claim 6, which comprises decomposing a cuprouschloride-trialkyl phosphite complex by reaction with sodium sulphide toliberate the trialkyl phosphite.

8. Process which comprises decomposing a cuprous halide-trialkylphosphite complex by a reagent which itself is capable of forming acomplex with the cuprous t 3 I halide, whichcomplex is more stable thanthe said cuprous halide-trialkyl phosphite complex and thus liberatesthe trialkyl phosphite.

9. Process which comprises decomposing a cuprous halide trialkylphosphite'complex with pyridine which forms a stable complex with thecuprous halide and liberates the trialkyl' phosphite.

10. Process which comprises decomposing a cuprous "2,897,224. r j phalide-trialkyl phosphite complex with an alkylcyanide unsubstitutedtriallgyl phosphite-cuprous halide complex 7 under a pressuresubstantially lower'thanatmospheric at a temperature suflicient to causedecomposition of said complex, said pressure being sufiiciently low thatsaid decomposition gives said trialkylphosphite as a principaldecomposition product. a

13. A process according to claim 12 wherein said pres- I sure is oftheorder of 0.1 to 0.5 mm. Hg abs.

14. A process for the production of lower unsubstituted trialkylphosphites which comprises subjecting a cuprous- "chloride-trialkylphosphite complex of the formula .(RO) P.CuCl, where R is a lowerunsubstituted alkyl group, to distillation in the form of a thin layerunder a pressure of the order of 0.1 to 0.5 mm. Hg abs. therebyproducing a trialkyl phosphite distillate.

15. A process of producing trimethyl phosphite which comprises heatingtrimethyl phosphite-cuprous chloride complex (CH O) P.CuCl,in a thinlayer at a temperature in the range of substantially C, to 220 C; and ata pressure in therange of substantially 0.1 to 0.5 mm. Hg abs., andcondensing the vaporsevolved- '16. A process for producing a lowerunsubstituted trialkyl phosphite which comprises reacting a,cuproushal-ide with phosphorus trichloride and a lower unsubstitutedalkanol to produce a cuprous halide-trialkyl phosphite complex thenheating said complex under a pressure substantially lower thanatmospheric at a temperature sufficient to cause decomposition of saidcomplex, said pres sure being sufficiently low that said decompositiongives said trialkyl phosphite as a principal decomposition product.

References Cited in the file of this patent l UNITED STATES PATENTSGruen et a1. ..---l. June .3, 1952 OTHER REFERENCESI Arbuzov: Chem. Abs,29, 2146 1935

1. PROCESS FOR THE PRODUCTION OF LOWER UNSUBSTITUTED TRIALKYLPHOSPHITES, WHICH PROCESS COMPRISES REACTING A CUPROUS HALIDE WITHPHOSPHORUS TRICHORIDE AND WITH A LOWER UNSUBSTITUTED ALKANOL TO PRODUCEA CUPROUS HALIDETRIALKYL PHOSPHITE COMPLEX AND SUBJECTING THE SAIDCOMPLEX TO CONTROLLED DECOMPOSITION UNDER CONDITIONS WHICH LIBERATE THETRIALKYL PHOSPHITE.